This invention relates to inhalers for medicaments, and more particularly, to inhalers with arrangements for breaking up agglomerates of dry powder.
In addition, of interest are PCT applications WO 90/13328 and WO 93/09832. These latter applications disclose various inhaler embodiments including impact release of medicament dosages. However, these embodiments involve relatively complex camming and similar arrangements which are costly to implement. These latter applications are also incorporated by reference herein.
Dry powder inhalers are used as drug delivery devices for administering pharmaceutical compounds to individuals. Some of these devices employ a pharmaceutical powder deposited on a substrate surface and sealed with a sealing layer. In other devices, the powder may be supplied in a reservoir and then transferred to a dose carrier one dose at a time. The substrate may be provided as a tape on a reel in cassettes or in cartridges, for example. When the patient requires medication, the ideal dry powder inhaler forms a fine particle cloud that is to be inhaled and thereby delivers a high respirable fraction of the stored dose deeply into the patients lungs. In most cases, the deep recesses of the lung is the desired site for the drugs in the inhaled powder cloud.
This can be most efficiently achieved by:
1. Releasing a high fraction of the deposited drug and
2. Insuring that the powder cloud consists of individual particles or particle aggregates between 1 xcexcm and 5 xcexcm.
As individual particles are reduced below 10 xcexcm, both release and particle aggregation become a serious hindrance to delivering a high respirable fraction deeply into the patient""s lungs.
A common problem addressed by various prior art inhaler apparatuses for dispensing dry powder medicaments is providing for a controlled reliable release of the medicament. The dry powder medicaments inhalers may be loaded with medicaments by filling techniques not involving electrostatics. In certain other implementations, the deposited powder tends to form agglomerated particles resulting in uncontrolled variation in the amount of medicament released. Several of the aforementioned applications provide various solutions to this problem.
Numerous approaches have been taken in the design of dry powder inhalers. In some cases, the powder is released by impact of a substrate powder carrier, as disclosed in WO 93/09832. Of interest is an inhaler as disclosed in WO 90/13328.
In copending applications Ser. Nos. 661,213 and 661,212, indentations or raised surfaces are disclosed in the inhaler interior surfaces having contact with the medicament for inhalation, the surfaces minimizing the area of contact between the medicament and the surfaces of the inhaler apparatus, promoting the release of the medicament from the inhaler.
When particles of medicament agglomerate, they impact the mouth and throat rather than remain in the air flow for deposition in the lungs. One remedy is to provide tortuous channels in the inhalers to promote deagglomeration. However, the medicament may be deposited along the channels leading to inaccurate dosage dispensing. Agglomeration also results in the inhaler tending to dispense the medicament inaccurately so that greater or lesser amounts are dispensed.
The small particle size, e.g., 2 xcexcm to 7 xcexcm, required for transport to the lung presents a number of problems for release by the inhaler and delivery to deep lung regions. As the particle size decreases, the relative bonding force between the particle and other objects increases. This applies to both particle-to-substrate bonding and particle-to-particle bonding. As a result, particle aggregates become more tightly bound and individual particles more difficult to remove from the substrate. Aggregation increases the effective size of the drug released and diminishes the respirable fraction. The increase in relative particle-to-substrate bonding makes drug release more difficult and also decreases the respirable fraction.
Additional investigation using ultrasonic frequencies to agitate the surfaces have been unsuccessful in removing particles below 10 xcexcm from a planar surface. There is a mismatch between the particle size and the wavelength of the substrate material in typical polymeric materials. The wavelengths of the material are a large multiple of the dimensions of the particles and does not provide efficient energy coupling. Acoustic frequencies above 100 MHz would be required for particle resonance to occur. Thus, either unrealistically high frequencies to minimize wavelength or high acoustic amplitudes to increase the force differential across the small particles are required.
The present inventors recognize a need for a drug inhaler delivery system for dry powder pharmaceutically active ingredients for breaking up such particle aggregation should they form. They recognize a need for delivery of microgram depositions in quantities ranging from about 10 xcexcg to the milligram range with a delivery accuracy of about 10%.
A medicament powder delivery device according to the present invention comprises a carrier having at least a flexible portion on which portion is deposited a discrete medicament dosage and means for imparting an energy pulse to the carrier flexible portion for deflecting the carrier portion and releasing the dosage from the deflected portion by momentum transfer.
In one aspect, the means for imparting an energy pulse comprises means for flexing and snap releasing the flexed carrier portion.
In a further aspect, the carrier portion includes a finger resiliently extending from a carrier base region, the means for imparting for flexing the finger relative to the base region.
In a further aspect, a body is included with a cavity for receiving the carrier portion and the means for imparting including an anvil with a bore therethrough fixed to the body in the cavity for receiving the snap released finger, the bore for receiving the released dosage, and including means for causing the finger to resiliently impact the anvil to rapidly decelerate the finger to provide the momentum transfer to the dosage.
In a further aspect, the dosage tends to form aggregates, the anvil including at least one channel, further including means coupled to the housing for creating an air jet stream through the at least one channel to disintegrate aggregations of the dosage during the impact.
In a further aspect, the finger is corrugated.
In a still further aspect, the finger extends in a given direction from the base region, the finger having corrugations extending along the given direction.
The means for creating the jet stream may include a further resilient finger overlying the carrier finger for initial resilient displacement coincident with initial displacement of the carrier finger, the displaced fingers for snap release in a second displacement, the further finger for creating the air stream during the second displacement.
In a further aspect, the further finger has a different spring constant than the carrier finger so as to accelerate slower than the carrier finger upon the snap release.
In a still further aspect, the carrier includes a first disc with a plurality of radially extending fingers, a dosage on each finger, and the means for imparting comprises cam means for snap flexing a selected finger to release the dosage on the selected finger.
Index means are preferably included for indexing the selected finger to a medicament release position for snap flexing the selected finger by the cam means.
The first disc may include a carrier disc with a plurality of first fingers each carrying a dosage, a spacer disc overlying the carrier disc with a plurality of second fingers overlying and corresponding to the first fingers and a ring with index holes and a third plurality of fingers over lying and corresponding to the first and second fingers, the spacer disc being bonded to the carrier and ring discs, the indexing means for selectively engaging the ring index holes.
Cam means are preferably provided for manually flexing the selected fingers.
The cam means may flex the first and second fingers past the third fingers.
In a further aspect, the carrier comprises a belt portion with a plurality of fingers extending transversely from the belt portion, each of the fingers having a separate dosage and arranged for selective resilient displacement relative to the belt portion.
In a still further aspect, drive means are included for displacing the belt to increment the fingers sequentially to a dosage release position.
The means for imparting may include a clamp for clamping the belt portion adjacent to a given finger and a deflecting member for selectively flexing and snap releasing the selected given flexed finger relative to the belt portion.
The carrier may comprise an element, the dosage comprising a plurality of discrete dosages in spaced relation on the element, the means for imparting including a carrier deflection member adjacent to the element, and means for momentarily bending and deflecting the element to momentum transfer release a selected dosage from the element upon release of the deflected element.
In a further aspect, means are included for selectively aligning successive dosages on the element to the deflection member.
In a further aspect, a core member is included and rotatable about an axis, the element comprising an array of fingers radially extending from the core member about the core member in a spiral about the axis, means selectively align and deflect each the finger to snap release a selected dosage from the selected finger by momentum transfer.
In a further aspect, the carrier comprises a spring finger for receiving a dosage and dosage substrate from a plurality of dosages and dosage substrates in a stack aligned one over another, and means are included for selectively placing successive dosages and dosage substrates on the carrier, the means for imparting including means for snap deflecting said finger against an anvil.